Think about riding a bike. What do you remember? Keep pedaling, since it's easier to balance when you're moving. Balance is important because falling hurts. Falling is an inefficient form of transportation. Being inefficient means your parents force you to walk slowly but eat while jumping up and down for the rest of the day to show you why efficiency is important.

Beside all that critical information, you remember the muscle memory. You remember how to pedal, balance, roll a fall and hide tears, and quietly run when no one can see you.

I started playing Starcraft 2 again. Intellectually, it all comes right back. I know to build a wall and what a bioball is and that I need to upgrade my units. The actual actions are another story. The rhythm is gone, so marines yell that they're ready to go and I don't have a second set already queued up a moment before. The clicking is all wrong, with selection failure and consequently, control groups are all wrong.

Some people wish they could go back to the past and tell their past selves what they know now. But as we all know, we didn't do dumb stuff because we didn't know better, we did it because we were stupid (the politically-correct term is "young"). The smart action is to go back and ask your past self what they know, since you're old and forgot. Alternatively, kidnap them and force them to play Starcraft for you.